Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$127.50	10.700%	$141.1425	$141.14	$141.15	$141.10
Purchase #2	$78.45	5.686%	$82.9107	$82.91	$82.90	$82.90
Purchase #3	$150.70	7.742%	$162.3672	$162.37	$162.35	$162.40
Purchase #4	$187.45	9.549%	$205.3496	$205.35	$205.35	$205.30
Purchase #5	$114.68	12.695%	$129.2386	$129.24	$129.25	$129.20
Purchase #6	$69.65	13.386%	$78.9733	$78.97	$78.95	$79.00
Purchase #7	$201.26	8.871%	$219.1138	$219.11	$219.10	$219.10
7 purchase totals =	$929.69		$1,019.0957	$1,019.09	$1,019.05	$1,019.00